This invention relates to linear actuators including those wherein a motor provides torque to rotate a shaft threadably carried to drive a piston mounted for linear movement within a cylindrical housing, and more particularly to a method of connecting opposed shafts utilizing a special coupling of minimal length.
Linear actuators having motors for driving lead screw arrangements are illustrated in U.S. Pat. Nos. 4,753,071 and 5,577,433. In devices of this kind, for example, connections between a motor shaft and a driven lead screw have heretofore required couplings of substantial length. Another problem is brought about by the need for mounting brackets or plates heretofore required for positioning such a motor housing, coupling apparatus, control components and cylindrical housing carrying an oscillatable piston. It would also be desirable to provide an improved coupling which would minimize the effects of any misalignment of the parts such as a power take-off shaft for transmitting torque to a lead screw threadably carried by a piston and aligned within a cylinder. The effects of misalignment are often compounded by temperature conditions which produce expansion and contraction of elongated components.
Accordingly, it is an important object of this invention to provide a method for connecting aligned shafts utilizing a longitudinal aligned insert preferably constructed of plastic which is preferably machinable. The insert receives overlapping end connections between the shafts. Because the insert is capable of a certain amount of forgiveness or yielding to compensate for misalignment, and may possess a low coefficient of expansion to reduce problems as result from thermal expansion and contraction of the parts a foreshortened coupling is provided which is especially useful in a linear actuator.